This invention relates generally to flooring tools, and in particular to loop pile cutters used to cut seams in carpets.
A loop pile cutter is commonly used in carpet seaming. Modern carpets are constructed with tufts of colored yarn material that are knitted in rows into a backing material by machines. The tufts form the “face” of the carpet, which faces up and is visible on the floor of a room. The backing faces down and holds the yarns together.
The carpet is manufactured in standard width rolls. The roll widths are cut to the dimensions of the room. In many cases, they are seamed together with a hot melt adhesive tape to form a single, one piece floor covering. In other cases, primarily in commercial settings, the carpet is glued directly to a subfloor with seams simply abutted. In either case, the quality of the installation depends on proper preparation of the edges of the carpet forming the seams.
The loop pile cutter prepares carpet edges for seaming by trimming the backing material as closely as possible to a row of carpet tufts. Without this trimming, the rough edges of backing can protrude past the tufts. This can create unsightly gaps at the seam. Loop pile cutters have a left blade and a right blade, which allow the tool to trim the carpet close to the tufts on both sides of the seam, greatly reducing such gaps.
As described in U.S. Pat. No. 3,543,400 to Scott, and U.S. Pat. No. 5,881,463 to Casteel, the distinguishing feature of a loop pile cutter (compared with other carpet seam cutters) is a blade holder that is adjustable in height in relation to a base. With reference to FIG. 1 of Scott, the base 14 is made with a supporting plate 12 with two L-shaped angle members 69 forming the base bottom. The base 14 rides on a subfloor. Supporting plate 12 has slot 38, and arm portion 18. Arm portion 18 has an inclined upper edge 20. Both slot 38 and upper edge 20 are formed at an acute angle of about 30 degrees in relation to the base 14. Slot 38 and upper edge 20 form the guide surfaces for the height adjustment of the blade holder.
The blade holder that fastens on the base 14 is formed with a pair of left and right retaining plates 24 welded to a guide plate 28 (FIG. 3) forming a center. Guide plate 28 forms carpet engaging edge 32 which guides the cutter between rows of carpet tufts.
The retaining plates are also riveted together along with handle 26 at two upper flat areas. As shown in FIG. 3, these flat areas are bordered by of two angled, upwardly jogging “shoulders” 25. The angle of the shoulders 25 corresponds to the upper edge 20 of arm portion 18 (FIG. 1) once the blade holder of this cutter is assembled onto base 14. Thus, shoulders 25 (FIG. 3) ride upon and are guided by the inclined plane defined by upper edge 20 of arm portion 18 (FIG. 1). As shown in FIG. 1, this incline defines a range of height adjustment for the blade holder in relation to the base 14.
As shown in FIG. 1, the blade holder has had two nuts 42 (not shown) welded onto a retaining plate outer surface. The nuts 42 (not shown) receive two threaded thumb screws 36, 64. Thumb screw 36 runs through slot 38 for to hold the blade holder at a selective height above base 14. When thumb screw 36 is tightened into a first nut 42, the inside of retaining plates 24 are clamped and frictionally held against the outside of supporting plate 12. This clamping action of thumb screw 36 holds the blade carrier at a height above base 14.
As shown in FIG. 5, blades 54, 56 are held on their outer surfaces by the inner walls of retaining plates 24. These inner walls form recesses 48, 50 (FIGS. 2 and 3). As shown in FIG. 5, blades 54, 56 are held on their inner surfaces by guide plate 28 that forms carpet engaging edge 32 (FIG. 1). Left and right blades 54, 56 are offset slightly from the centerline of the cutter by a half thickness of guide plate 28.
As further shown in Scott's FIG. 1, a second thumb screw 64 is threaded into a second nut 42 (not shown) welded onto a retaining plate outer surface. Thumb screw 64 serves primarily to adjustably hold left and right blades 54, 56 (FIG. 3) within blade recesses 48 and 50 (FIGS. 2 and 3). The angle of blade recesses 48 and 50 (FIG. 2) in relation to base 14 is the same 30 degree angle as upper edge 20 of arm portion 18 and slot 38 for height adjustment.
The reason that the blades 54, 56 must be adjusted in height within the area defined by blade recesses 48, 50 (FIG. 2) is as follows: The blade holder must be moved up or down to accommodate various thicknesses of carpet. As the blade holder is moved up or down on upper edge 20 of base 14, blades 54, 56 must be correspondingly extended or retracted so that they may seat within a recesses 58 in base 14 (FIG. 1). As shown in FIGS. 1 and 3, recesses 58 keep blades 54, 56 from deflecting horizontally due to resistance from the carpet.
Deflection of the blades themselves could result in the cutter shearing off parts of carpet tufts which are meant to be preserved, or could also result in carpet backing material not being trimmed. To produce the best looking seam, both these problems must be avoided. Hence, all the loop pile cutters discussed herein have blade holders similar to recesses 48, 50 (Figure and 3) and recesses 58 (FIGS. 1 and 3) to prevent deflection of the blades.
As further shown in Scott's FIG. 1, the approximately 30 degree angle formed by blade recesses 48 and 50 (FIG. 3), the inclined upper edge 20 of support plate 12, and slot 38, are designed to place the blades 54, 56 approximately at a 30-degree angle in relation to carpet entering at carpet receiving slot 34. This angle is preferred because it exposes a long surface of blades 54, 56 where the cross section of the carpet backing is expected to pass. A lower angle may cause the carpet tufts to trap under the blade and be sheared. A higher angle would place less blade surface in the area of the carpet backing, resulting in faster blade wear, less efficient cutting, both of which can cause the carpet to rise up and wad against carpet engaging edge 32.
Thus, the loop pile cutter of Scott provides a base and a blade holder that is adjustable in height. As shown in FIG. 1, a carpet edge to be trimmed enters a carpet receiving slot 34 defined as the open area between the edge referred to as carpet receiving slot 34 of base 14 and the lower edge of carpet engaging edge 32. The height adjustment allows carpets of various thicknesses (varying by height of tufts and thickness of carpet backing) to enter carpet receiving slot 34. Carpet engaging edge 32 guides the cutter between two rows of carpet tufts as the user pushes on handle 26 (FIG. 1).
In use, as shown in FIG. 1, first the height of the blade holder must be adjusted such that carpet engaging edge 32 of guide plate 28 (FIG. 5) presses deep between two rows of carpet tufts all the way down to the carpet backing (best seen in FIG. 5). Thumb screw 36 is tightened to hold this height.
Regarding the selection of the left blade 54 and right blade 56, the directional terms left and right in the disclosure of Scott are made from the perspective of section 3-3 facing down carpet engaging slot 34 in the direction of the blades. As shown in FIG. 4, a left blade 54 is extended into a recess 58 (FIG. 1) in base 14 in order to trim close to a left side of a carpet tuft (making “cut” 78). In such case, a right blade 56 is retracted (raised up) into blade recess 50 (FIG. 3) so that it will not cut any carpet. Alternatively, as shown in FIG. 5, a right blade 56 is extended into a recess 58 (FIGS. 1 and 3) to trim close to a right side of a carpet tuft (making cut 80). In such case, a left blade is 54 is retracted (raised up) into a recess 48 so that it will not cut any carpet. With both edges of the carpet prepared in this manner, the carpet tufts should abut precisely with no gap due to excess carpet backing. This produces an improved carpet seam.
However, as the loop pile cutter of Scott is pushed through a row of carpet, the carpet engaging edge 32 (FIG. 1) encounters side loads from carpet tufts which resist being parted. As shown in FIG. 3, to the extent that there is play between side plates 24 and upper arm 18 of base 12, these side loads can cause shifting of the entire blade holder to the left or right off the centerline of base 14. The side loads can also cause bending of supporting plate 12. This shifting of the components and bending of the main base bracket component (supporting plate 12) will be referred to as deflection of the blade holder. Deflection of the blade holder can cause the cutter to turn to the left or the right as it moves between the rows of tufts. This can cause the cutter to shear tufts close to the blade, or even skip out between the rows of tufts which are intended, into another adjacent set of tuft rows. If such skipping occurs, the edge will not match with another properly cut edge, and the trimming operation on the improperly cut side must be repeated.
With the cutter of Scott, as shown in FIG. 1, the cutter's main resistance to deflection is the clamping action of thumb screw 36 holding retaining plates 24 against arm portion 18 of supporting plate 12. Only one thumb screw is provided to produce all necessary clamping force, and the position of this screw is at considerable distance from side loads that cause the deflection. Some means of reducing the deflection of the blade holder assembly would tend to reduce the undesirable shearing of tufts or skipping out of tuft rows that may occur.
Another loop pile cutter with a different blade holder construction is disclosed in U.S. Pat. No. 5,881,463 to Casteel. As shown in Casteel's FIG. 2, the loop pile cutter has a similar base 102 and a mounting bracket 104. Mounting bracket 104 has an open-ended slot 114 for holding a blade carrier, and a second slot 112, which is closed-ended. The angle formed by the centerlines of both slots 112, 114 in this cutter is the same 30 degree angle as in Scott.
As shown in FIG. 1, blade support 300 is an assembly forming the blade holder of this cutter. Blade support 300 includes a center plate 301 (FIG. 8). As shown in FIG. 8, center plate 301 has a tongue 302. Tongue 302 has also has a centerline at a 30 degree angle in relation to its bottom edge. This makes tongue 302 insertable into open-ended slot 114 of mounting bracket 104 (FIG. 2). Tongue 302 can thus be slideably positioned on the incline of open-ended slot 114 (FIG. 2). As shown in FIG. 1, this allows blade support 300 to be positioned at a selective height above base 102 (FIG. 2). As shown in FIG. 8, center plate 301 also has a hole 306 for passage of a threaded fastener.
To form the blade holders of this cutter, as shown in FIGS. 9 and 10, bar spacers 308, 308′ and nose spacers 310, 310′ are attached (as by welding or riveting) to either side of center plate 301. The bottom edges of bar spacers 308, 308′ form top bearing surfaces 312, 312′. These define the top boundary of the left blade compartment 319 and right blade compartment 319′ (FIG. 13), respectively. The top edges of nose spacers 310, 310′ form bottom bearing surfaces 314, 314′. These define the bottom boundary of the left blade compartment 319 and right blade compartment 319′ (FIG. 13), respectively. As with blade recesses 48 and 50 of Scott, left blade holder 319, and right blade holder 319′ hold the blade at about a 30 degree angle in relation to base 14.
As shown in FIG. 13, left side plate 316 and right side plate 316′ are mounted as by riveting or welding onto bar spacers 308, 308′ and nose spacers 310, 310′. Left side plate 316 and right side plate 316′ define the outer boundary of left blade compartment 319 and right blade compartment 319′. As shown in FIGS. 11 and 12, the left side plate 316 and right side plate 316′ additionally have “openings” that align with hole 306 through center plate 301 (FIG. 8).
As shown in FIG. 1, threaded fastener 10 may pass through the “openings” in side plates 316, 316′ (FIGS. 11 and 12), though hole 306 (FIG. 8) in the center plate, and then be threaded into in a nut (not shown) attached to a side plate outer surface. As shown in FIG. 1, tightening the threaded fastener 10 holds the blades 14, 14′ at a height within the blade support assembly 300.
Bar spacers 308, 308′ and nose spacers 310, 310′ (FIGS. 9 and 10) serve one additional function in that, once attached to center plate 301 (FIG. 8) and left side plate 316 and right side plate 316′ (FIGS. 11 and 12), they hold all these components together if threaded fastener 12 (FIG. 1) is removed. As shown in FIG. 1, this is helpful if blade support assembly 300 must be removed from base 102 (FIG. 2). This may be required during maintenance or cleaning of the cutter.
As shown in FIGS. 11 and 12, left side plate 316 and right side plate 316′ additionally have holes 318, 318′ respectively for insertion of a second threaded fastener 12 (FIG. 1). Threaded fastener 12 (FIG. 1) passes through a hole 318 in left side plate 316 (FIG. 12), slot 112 in mounting bracket 104 (FIG. 2), hole 318′ in right side plate 316′ (FIG. 11), and threads into a nut (not shown) mounted on a side plate outer surface. As shown in FIG. 1, when threaded fastener 12 is tightened, the inner surfaces of left and right side plates 316, 316′ (FIGS. 11 and 12) are clamped and frictionally held against mounting bracket 104 of base plate 100 (FIG. 2), holding blade support 300 (FIG. 1) at a selective height.
The cutter of Casteel has the same or worse problems of deflection of its blade holder. As shown in FIG. 1, threaded fastener 12 provides the only resistance to side loads, but is again at a distance from the outer end of blade support 300 (element 18). The loop pile cutter also includes bar spacers 304, 304′, and nose spacers 310, 310′ (FIGS. 9 and 10) forming the blade compartments. These actually tend to hold left side plate 316 and right side plate 316′ (FIGS. 11 and 12) apart. This creates built-in play between the inner surfaces of left side plate 316 and right side plate 316′ (FIGS. 11 and 12) and mounting bracket 104 (FIG. 2). As a result, threaded fastener 12 is less able to clamp the inner surfaces of left side plate 316 and right side plate 316′ (FIGS. 11 and 12) against mounting bracket 104 (FIG. 2).
Furthermore, as shown in FIG. 2, slot 114 which accepts tongue 302 of center plate 301 (FIG. 8), is open-ended. In use, as blade support assembly 300 (FIG. 1) encounters resistance from carpet tufts and begins to deflect, the open-ended shape slot 114 of promotes bending of mounting bracket 104. If this open-ended slot 114 were closed-ended, the bending resistance of mounting bracket 104 may be improved, and blade support assembly 300 would have greater resistance to deflection.
As shown in FIG. 12, open-ended slot 114 (FIG. 2) is formed with an open end so that tongue 302 of center plate 301 (FIG. 8) of blade holder assembly 300 (FIG. 1) can be removed entirely from open-ended slot 114 (for maintenance, for example). Open ended slot 114 is economical in that no additional parts are required to provide the functions of a holder and an inclined plane for adjustably mounting blade holder assembly 300. However, open ended slot 114 promotes bending of mounting bracket 104.
Therefore, for several reasons, blade support 300 of the loop pile cutter of Casteel may deflect even more under side loads than the blade holder of Scott.
Another prior art loop pile cutter with a different blade holder construction, manufactured by Crain Cutter Company, is shown in FIG. 1 of this application. Loop pile cutter 10000 has a base 10200 with a base mounting bracket 10205. As shown in FIG. 2, base mounting bracket 10205 includes an open ended slot 10210, a blade holder screw slot 10215, a flat 10220, and bottom edge 10225. The centerlines of open ended slot 10210, blade holder screw slot 10215, as well as the angle formed by bottom edge 10225, all form an approximately 30 degree angle in relation to a base bottom surface 10230 of base 10200.
The exploded view of blade holder 10500 in FIG. 2 shows holder right side 10505, holder center 10540, and holder left side 10570. Holder right side 10505 includes right inward jog 10510, right spot weld surface 10515, right partial pierce 10520, right hand attached nut 10525, and a blade holder screw through hole 10530. Holder left side 10570 includes left inward jog 10575, left spot weld surface 10580, left partial pierce 10585, left hand attached nut 10590, and a blade thumbscrew passage hole 10595. Right inward jog 10510 and left inward jog 10575 are also at a 30 degree angle in relation to base bottom surface 10230 once assembled onto base 10200. Holder center 10540 includes a center row guiding edge 10545, and a center blade screw passage hole 10550.
Blade holder 10500 is assembled by spot welding blade holder center 10540 between holder right side 10505 and holder left side 10570 at right spot weld surface 10515 and left spot weld surface 10580. After spot welding, holder right side 10505 and left side 10570 abut one another at right partial pierce 10520 and left partial pierce 10585.
The function of the abutting surfaces formed by right partial pierce 10520 and left partial pierce 10585 is to produce an inexpensive pair of guide surfaces on both parts, which is insertable within open ended slot 10210. Once inserted into slot 10210, these guide surfaces serve to guide the height adjustment of blade holder 10500 at an angle of approximately 30 degrees in relation to base 10200.
As shown in FIG. 1, blade holder center 10540, once spot welded together with holder right side 10505 and holder left side 10570, forms the center row guiding edge 10545 of the cutter, as well as blade pocket separator 10555.
As shown in FIG. 2, right inward jog 10510 of holder right side 10505 forms the bottom of right blade pocket 10535. Left inward jog 10575 of holder left side 10570 forms the bottom edge of a left blade pocket 10600. Bottom edge 10225 of base holder bracket 10205 forms the top of both right blade pocket 10535 and left blade pocket 10600.
Right slotted razor blade 10625 is held in right blade pocket 10535, and left slotted razor blade 10650 is held in left blade pocket 10600. Right slotted razor blade 10625 and left slotted razor blade 10650 are held at a selective height within right blade pocket 10535 and left blade pocket 10600 by blade thumb screw 10675. Blade thumb screw 10675 passes though blade screw passage hole 10595 of holder left side 10570, through the slot of left slotted razor blade 10650, through center blade screw passage hole 10550, through the slot of right slotted razor blade 10625, and threads into right hand attached nut 10525. Thus, when blade thumbscrew 10675 is tightened, blade holder right side 10505 is drawn inward to clamp and frictionally hold right slotted razor blade 10625 at a height. The blade thumbscrew head bottom 10676 of holding thumbscrew 10675 tightens down on the outer face 10651 of left slotted razor blade 10650 to frictionally hold left slotted razor blade 10650 at a height.
Blade holder thumb screw 10400 passes through a blade holder screw through hole 10530 in holder right side 10505, a holder slot 10215 in base mounting bracket 10205, and threads into a left hand attached nut 10590. Thus, as lower holder thumbscrew 10400 is tightened, holder right side 10505 and holder left side 10525 are drawn together and frictionally held against flat 10220 of base mounting bracket 10205. As shown in FIG. 1, thumb screw 10400 provides the cutter's main resistance to side loads at row guiding edge 10545 causing deflection of blade holder 10500.
Much as with the cutters of Scott and Casteel, as shown in FIG. 1, blade holder thumb screw 10400 is at a distance from center row guiding edge 10545, which reduces its ability to resist deflection. Much with as the bar spacers 308, 308′ and nose spacers 310, 310′ (FIGS. 9 and 10) of Casteel, the abutting left partial pierce 10520 and right partial pierce 10585 work as a permanent separator between holder left side 10505 and holder right side 10570. As shown in FIG. 2, this separation further reduces the ability of body holder screw 10400 to effectively clamp holder right side 10505 and holder left side 10570 against base holder bracket 10205. The result is that the blade holder can deflect. Much as with the cutter of Casteel, open ended slot 10210 promotes bending of base mounting bracket 10205, further reducing the ability blade holder 10500 to resist deflection.
What is needed is a loop pile cutter with an improved blade holder assembly and blade holder mounting bracket in its base that can better resist deflection.